Method for making finned tubes



Feb. 16, 1954 E. BRUEGGER METHOD FOR MAKING FINNED TUBES 2 Sheets-Sheet 1 Filed Dec. 23, 1948 BY Z m mm ATTORN EYS E. BRUEGGER METHOD FOR MAKING FINNED TUBES Feb 16, 1954 2 Sheets-Sheet 2 Filed Dec. 23, 1948 ATTORNEYS Patented Feb. 16, 1954 rom *product.

mains.

i his 'invention relates to methods a m-makin 5 heat-transfer tubes having "an extended siirface ""in't'he' form of aspirallywoundifin The principal object of"the invention 'isff'to provideamethod formaking a heat=transferelent ofthis character wherein the fin'isfitted "to 'fthe tube by the pressure 'of the fin against the tube surfacefwhich*pressure, due to the method 'offmanufacture, "is sufficient to produce a "heattransfer union "equal to that obtainable by "embedding the edge of the 'fin in the metal of the f'ftube wall in the manner shown,forexar'nple, in 111.11 3. Patent No.'"1,'6' 68;5 34, dated May'l, 1928, to Berg, f'The method of "this application' is particula'rly'advantageouswhere'the fin is of soft *rnet'alsuch as aluminumwhich is difficultto w'ind 'g sjufiic ientlytight by'the'us ual winding methods toproduce'a satisfactory heat-conducting joint.

A further object of the invention is to. provide a" timed 'h'eat transfer "tube wherein the tube "V'VaIIlsnOt weakened by grooving, Iscoringor any deformation, making it more liable to .rupture from internal or ext'ernallpressure or mechanical stress,

inffurther object of "the invention ls'to provide a method of making heat-transfer elements of "fthekind described, whichmethod'isIcharacterized 'fby low cost, "high rate of production and a uni- Inthe accompanying drawings :1 have illus- :"trated the successivesteps followed in the" manu- "facture of said tube in accordance with the best methods now known to me.

, I'hat' e "also illus- "trated the "essential elements of the apparatus required to carry the process into effect.

"i "In said drawings,

Figz'l'shows the'precoil'edlfin as it isusedin one 'inethod herein described;

Fig."2 showsthe second step invthe process eni- *ploying'.the'precoiled fin illustrated in Fig. '1;

I F g; 3? shows the third step in the process;

Fig.4 is 'a'transverse sectlonon line 4- 4 of Ir s.

" Fig. 5 is anenlarged section of a niade'by ""theme'thod illustrated in'Figs. 1 to 4 showing particularly the heat-transfer union between" the tubeand fin;

Figs. 6 and '7 show the successive steps of a process: similarto 'that'shown'in"1"igs."1 to =14, but

wherein two ofthe steps arecombined into a single operation; 7 I

Fi'gfB is ,a section on line-"8+8 of Figg'i; fFig's. 9 and 10 showthesuccessive stepsbt a further modification; f Fig. 11- is "an enlarged perspective View of a modified form of fin whichmaybe advantageous- ;iy' employed particularly for wide fins;

( Fig, 12 is a longitudinal sectional view showing the application of the finof Fig, 11 to 'the"tube;

and

Fig.1?! isasection' an nn'e -|-3=*-1s'or Fig. 1-2. Referring to "the' drawings, :pa'rtibularlyto Fig. L1,?my' improved; heat 'trans'fenelement con'iprises a "continuous? tube 1 "for the'c'irculation of the liqaround Said tube to form' an extended meattransfer surface which depends "for its effi'c'ien'cy onjthe rate of heat transfer from themetal ofthe tube I through'the' joint 3 at'the base of thefinl.

In carrying outithelpro'cess as disclosed in Figs. l to 4, inclusive, the ribbon forming'the first'p'r'ecoiled as'shown i'nFig. 1 in the form of a continuous helix which hasits radia1'b1aneatian angle tothe axis of the henx 'so thatWhen the coiled fin is extended along the tube, as suown in ,Fig. 2, the plane of the surfaceo'f Ith'e 'hlix'lwlll be at an angle to the axis'of the tube.

In the manufacture of 'my improvedfheab transfer element the tube may -be supplied in continuous lengths or inprevio uslycutsections.

Likewisethe helically coiled fin material maybe supplied continuously-or in sections-of-a length tocorrespondwith-the-lengths of tube tObGSllbplied. After forming the-helix and extending -it along the tube asshown in Fig. 2, the metal forming the helix is turned upwardinto position :Where the'plane of-the ribbon is normal tothe axis of -the tube as shown in Figs. -3 and'4. This operationmayreadily be accomplished by ar-succession 'of rollers 4 such "as here shown wherein the axes-of the rollers are successivelyiat'different -"angles-'to the axis ofth'e tube with'the final -pair -iof-rollers normal thereto.

The effect of this operation is to-further reduce the diameter of the int'ernal bore of the helix 'so "'that' the metal of the fin-is pressed into the'rrletal 'of'the 'tubeto such an extent as to deform 'the.

softer metaland'put the two contacting's'urfac'es "under permanent compression tothereby provide 'a-heat-transfer contact of high heat-transfer efilci'ency.

' In"Fig.5 I "have diagrammatically illustrated "the -actionthat takes place" as themetal-at ithe base of the fin is compressedagainst thefmtal "of 4 the tube. The base of the =fin -as illustrated at- 5*is"rnushroomed out as showmandprssd "into the metalpf'the tube-"which 'is'therebycmpi'essefd as indicated by the 'stip'pled areas 6 the relat ve def ormation of the tube" and fin d'bellfling on'tne 'i'elative' hardness of the "metal "or fwhichthey are made.

The h'eattra'nsfer' element produced by "the ve described process is quite as efficient 'as 55 heat-transfer elements of the same dimensions manufactured in accordance with the Borg Patent No. 13668534. In'addition, "thehea't-trans- "fer element? of thep'resent application "has the advantage that the tube material is riot-{we s- -ene'd by grooving andthe cost of operation of pro-coiling and applying the fin is considerably less than that required for producing a similar quantity of the Berg tube. Both the Berg machine and the machine used for carrying out the present process are wholly automatic in their operations but a machine capable of successfully carrying out the improved process may be operated at a much higher rate of speed than the Berg machine wherein the metal of the tube must be grooved in orderto receive the edge of the fin material.

As shown in Figs. 3 and 4, the tube is supported on a mandrel 3 which is continuously rotated and may also be shifted longitudinallyat a rate corresponding to the pitch of the helix of the fin of the finished tube, the rollers 4 being supported on a stationary base adjacent the mandrel. If desired the mandrel may be rotated but not shifted longitudinally and the rollers 4 mounted on a longitudinally moving carriage alongside the mandrel; both types of machines are old in the art and either type may be satisfactorily employed for carrying out the present process.

In Figs. 6, 7 and 8 I have illustrated a modification of the above described process. As here shown a closely coiled length of fin, Fig. 6, is placed on the tube without extending the helix in the manner shown in Fig. 2. The mandrel is rotated and shifted longitudinally with respect to a pair of rollers 8 supported alongside the mandrel with their axes radial to the axis of the mandrel and with their adjacent surfaces spaced apart a distance equal to the thickness of the fin. The leading end of the ribbon is soldered to the tube wall and the ribbon threaded between the rollers. As the tube is rotated and shifted axially past the rollers the fin is straightened up to radial position and the coils spaced to the desired distance apart. the fin is straightened up to radial position the edge of the fin is pressed into the metal of the tube in the manner illustrated in Fig. 5.

In Figs. 9 and 10 I have illustrated a further modification of my invention. As here shown the ribbon is coiled simultaneously with its application to the tube. To this end the flat ribbon is fed into the machine through a pair of guide rollers 9 and thence coiled around the tube with its surface, in a direction across the Width of the ribbon at an angle to the tube wall as in the previously described procedures. Supported adjacent the mandrel which rotates and shifts axially as previously described, is a frame 10 carrying a series of rollers ll extending around a quarter turn of the tube and with their axes radial to the axis of the tube. As the tube is moved longitudinally past the frame It the turn of the fin which has just been coiled around the tube will be straightened into radial position, forming a good heat-conducting union with the tube as shown in Fig. 5.

In Figs. 11, 12 and 13 I have illustrated a further modification of my process, particularly suitable for wide fins. As here shown the fin is not formed of a flat ribbon as in the previously described processes, but instead the pre-coiled fin I2 is throughout the major outer portion of its width radial to the axis about which it is coiled but at its inner edge is bent away from the radial plane to an angle of about degrees thereto as shown at 53. To apply the above described fin to the tube I provide a base M which is moved longitudinally with respect to the tube as above described, the base having two sets of arcuately disposed rollers 15 adapted to receive the edge l3 of the fin between and straightening g the fin so that through the entire width it is radial to the axis of the tube. To this end the rollers of the two sets converge in the direction of rotation of the tube as more fully shown in Fig. 12.

It will be understood that Whereas I have disclosed several embodiments of my invention and the best methods and apparatus now known to me for carrying the invention into effect, the invention is not limited to the specific examples herein described but covers all such modifications thereof as fall within the scope of the appended claims.

I claim:

l..The method of making finned tubing which consists in forming a coil of a ribbon of metal about a tube in the form of a helix with the plane of a portion of the width of the ribbon inclined at a substantially uniform angle to the axis of the tube and with the inner edge of the helix unsecured to the tube wall and then bending such portion of the ribbon progressively to a plane substantially normal to the axis of the tube to thereby press the inner edge of the helix against and secure it to the wall of the tube to form a good heat-conducting joint therewith.

2. The method of making finned tubing which consists in forming a coil of a ribbon of metal about a tube in the form of a helix with the plane of the ribbon inclined at a substantially uniform angle to the axis of the tube and with the inner edge of the helix unsecured to the tube .wall and then bending the ribbon to a plane substantially normal to the axis of the tube to thereby press the edge of the helix against and secure it to the wall of the tube to form a good heat-conducting joint therewith.

3. The method of making finned tubing which consists in coiling a ribbon of metal in the form of helix with the plane of the ribbon uniformly inclined to the axis of the helix throughout the helix, assembling the helix on the tube with the inner edge of the helix unsecured to the tube wall and then progressively bending the ribbon to a plane substantially normal to the axis of the tube to thereby press the edge of the helix against and secure it to the wall of the tube to form a good heat-conducting joint therewith.

4. The method of making finned tubing which consists in advancing a ribbon of metal toward the tube with its surface at an angle to the axis of the tube, rotating the tube to coil the ribbon about the tube in the form of a helix with the plane of the ribbon uniformly inclined to the axis of the tube without securing the inner edge of the helix to the tube and bending the ribbon to a plane substantially normal to the axis of the tube to thereby press the inner edge of the helix against the wall of the tube to secure it to the tube and to form a good heat-conducting joint therewith.

ERNEST BRUEGGER References Cited in the file 'of this patent .1

UNITED STATES PATENTS Date Wallace June 1, 1948 

